1. Field of the Invention
The present invention relates to an automatic focusing apparatus of a camera and, more particularly, to an automatic focusing apparatus of a camera, which can perform continuous photographing while changing a photographing distance with respect to objects to be photographed in a single picture on the basis of information concerning a distance to an object to be photographed detected by a focus detect device.
2. Related Background Art
In order to photograph an object to be photographed having a depth exceeding a depth of field corresponding to a depth of focus of a photographic lens, a conventional auto focus (to be referred to as "AF" hereinafter) camera includes a multi-distance measuring apparatus for measuring distances to objects to be photographed located in a plurality of areas in a field to obtain measured distance values for the respective objects to be photographed.
In a camera of this type, a focusing position of a lens is determined only once on the basis of a measured distance value corresponding to a closest object to be photographed or an average value of measured distance values corresponding to objects to be photographed in a plurality of areas, and the lens is driven to this focusing position to perform photographing.
In photographing, a user normally depresses a release button to the first stroke, confirms through a finder that a lens is focused on a desired object to be photographed, and then depresses the release button to the second stroke to perform photographing. If the user is a beginner not knowing such a way of confirmation, however, focusing on a desired object to be photographed may not be performed by one photographing operation as described above, and an undesired photograph may be taken. In addition, in photographing performed by remote control or using a self-timer, a user cannot check whether a lens is focused on a desired object to be photographed. In such photographing, therefore, an out-focus shot or photograph may be taken by one focusing operation as described above.
Japanese Patent Laid-Open No. 63-17417 discloses a conventional automatic focusing apparatus of this type.
In this apparatus, a plurality of focus detection areas are provided in a field, a focus condition of a lens with respect to an object to be photographed in each area is detected, and an object on which the lens is to be focused can be selected from the objects to be photographed in the respective areas upon operation of an operating member. By operating a release button after an operation of selecting a predetermined object to be photographed on which the lens is to be focused is performed, the lens is driven to a focus position for focusing the lens on the object to be photographed.
In the above conventional apparatus disclosed in Japanese Patent Laid-Open No. 63-17417, however, an object on which the lens is to be focused must be determined before photographing, i.e., before a depressing operation of the release button to the first stroke. Therefore, the following problem may be posed in photographing. That is, for example, assume that a user performs an operation for selecting a far object to be photographed on which the lens is to be focused and then performs a depressing operation to the first stroke while viewing the object to be photographed through a finder. In this case, if the user changes his or her mind by checking a composition obtained when the lens is focused on the far object to be photographed and determines to focus the lens on a close object to be photographed, he or she must re-operate the operating member after canceling the depressing operation to the first stroke and re-perform the depressing operation to the first stroke, resulting in poor operability.
Another conventional automatic focusing apparatus of a camera detects a focus condition of an object to be photographed in a field central area by a focus detect device, calculates a defocus amount to a focus position of a lens on the basis of a detection result of the focus condition, and drives the lens to the focus position in accordance with the calculated defocus amount.
In this camera with the above conventional automatic focusing apparatus, the lens is driven to perform photographing on the basis of only one defocus amount detected by the focus detect device. Under such control based on one defocus amount, however, if a main object to be photographed is much smaller than a picture or has a large depth, an object to be photographed desired by a user and that determined by the camera do not always coincide with each other. As a result, a photograph in focus with an object that the user intended may not sometimes be taken.
In addition, when a user is a beginner or photographing using a self-timer, a main object to be photographed often falls outside a focus detection area of a camera. Therefore, it is sometimes difficult to take a photograph reliably in focus with the main object to be photographed.